How do I calculate motor full-load current?

You do not — you look it up. NEC Table 430.250 tabulates full-load current by horsepower and voltage, and the Code requires those values for conductor and protection sizing. The nameplate current is used only for sizing the overload relay.

Why is the table current different from my motor's nameplate?

Because the table is a worst-case figure covering any motor of that rating, while the nameplate reflects your specific motor. A high-efficiency motor usually draws less than the table value, but the circuit is still sized from the table so a future replacement does not overload it.

Why does three-phase current drop with voltage?

Because power is roughly voltage times current times the power factor times √3 for three-phase. Doubling the voltage halves the current for the same power, and the table shows it: a 10 HP motor draws 28 A at 230 V and 14 A at 460 V.

What is the 125% for?

Branch-circuit conductors for a motor must be sized at 125% of the table's full-load current, which provides margin for the motor operating above its rated current at the extremes of voltage tolerance. The disconnect and short-circuit protection are sized from the same starting figure.

Why are there no single-phase motors above 10 HP?

They are not tabulated because they are not commonly manufactured — large motors are almost always three-phase. Where a large single-phase motor is used, the manufacturer's data and the applicable Code provisions for unlisted motors apply.

Motor Full-Load Current

Full-load current by horsepower and voltage for single-phase and three-phase motors, with the 125% figure used for conductor and overload sizing.

Data verified 2026-09-29 · based on NEC 2023 (NFPA 70-2023)

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Full-Load Current in Amperes (NEC Table 430.250)

Horsepower^[2]	115 V 1φ A^[2]	230 V 1φ A^[2]	208 V 3φ A^[2]	230 V 3φ A^[2]	460 V 3φ A^[2]	575 V 3φ A^[2]	125% of 460 V A^[1]
0.5 #	9.8	4.9	2.4	2.2	1.1	0.9	1.375
0.75 #	13.8	6.9	3.5	3.2	1.6	1.3	2
1 #	16	8	4.6	4.2	2.1	1.7	2.625
1.5 #	20	10	6.6	6	3	2.4	3.75
2 #	24	12	7.5	6.8	3.4	2.7	4.25
3 #	34	17	10.6	9.6	4.8	3.9	6
5 #	56	28	16.7	15.2	7.6	6.1	9.5
7.5 #	80	40	24.2	22	11	9	13.75
10 #	100	50	30.8	28	14	11	17.5
15 #	—	—	46.2	42	21	17	26.25
20 #	—	—	59.4	54	27	22	33.75
25 #	—	—	74.8	68	34	27	42.5
30 #	—	—	88	80	40	32	50
40 #	—	—	114	104	52	41	65
50 #	—	—	143	130	65	52	81.25
60 #	—	—	169	154	77	62	96.25
75 #	—	—	211	192	96	77	120
100 #	—	—	273	248	124	99	155
125 #	—	—	343	312	156	125	195
150 #	—	—	396	360	180	144	225
200 #	—	—	528	480	240	192	300
250 #	—	—	675	604	302	242	377.5

These are Code table values, not nameplate values. A motor's nameplate current may be lower than the table figure, and the Code still requires the table value to be used for conductor sizing — the intent is that the circuit accommodates any motor of that rating, not just the efficient one installed today.

Single-phase motors above 10 HP are not tabulated because they are not commonly manufactured. Three-phase current falls roughly in proportion to voltage: 460 V draws half of 230 V, and 575 V draws about 40%.

The 125% column is the branch-circuit conductor and disconnect sizing figure for a motor with a marked temperature rise of 40 °C or less. Motors with higher temperature rise use different factors, and the overload relay is sized separately from the motor's nameplate service factor.

Why the Code Uses Table Values

Motors of the same horsepower vary widely in efficiency, and therefore in current. An older standard-efficiency motor may draw 20% more than a premium-efficiency one of the same rating. If circuits were sized from the nameplate, replacing a motor with a less efficient one would overload the existing circuit.

Using a single tabulated figure for each horsepower and voltage means the circuit is adequate for any motor of that rating, and a swap does not require rewiring. The cost is that a modern high-efficiency motor leaves capacity unused — which is the intended trade.

The practical consequence: the branch circuit, disconnect and short-circuit protection are all sized from the table, while the overload relay is sized from the nameplate. That split is deliberate — the overload relay protects the specific motor, and the circuit protects the wiring.

Frequently Asked Questions

How do I calculate motor full-load current?: You do not — you look it up. NEC Table 430.250 tabulates full-load current by horsepower and voltage, and the Code requires those values for conductor and protection sizing. The nameplate current is used only for sizing the overload relay.
Why is the table current different from my motor's nameplate?: Because the table is a worst-case figure covering any motor of that rating, while the nameplate reflects your specific motor. A high-efficiency motor usually draws less than the table value, but the circuit is still sized from the table so a future replacement does not overload it.
Why does three-phase current drop with voltage?: Because power is roughly voltage times current times the power factor times √3 for three-phase. Doubling the voltage halves the current for the same power, and the table shows it: a 10 HP motor draws 28 A at 230 V and 14 A at 460 V.
What is the 125% for?: Branch-circuit conductors for a motor must be sized at 125% of the table's full-load current, which provides margin for the motor operating above its rated current at the extremes of voltage tolerance. The disconnect and short-circuit protection are sized from the same starting figure.
Why are there no single-phase motors above 10 HP?: They are not tabulated because they are not commonly manufactured — large motors are almost always three-phase. Where a large single-phase motor is used, the manufacturer's data and the applicable Code provisions for unlisted motors apply.

Value Sources

Each data column on this page is tied to the source it came from. The numbers in square brackets correspond to the table headers above.

#	Source	Type	Revision / method
[1]	Value computed from the standard's defining relationship	derived	Computed at build time from the defining formula and checked against every row.
[2]	NEC Table 430.250 — Full-Load Current, Three-Phase Alternating-Current Motors	standard	NEC 2023 (NFPA 70-2023)

Data Sources

Standard	Revision	What it covers on this page
NEC Table 430.250 — Full-Load Current, Three-Phase Alternating-Current Motors	NEC 2023 (NFPA 70-2023)	the three-phase columns
NEC Table 430.248 — Full-Load Current, Single-Phase Alternating-Current Motors	NEC 2023 (NFPA 70-2023)	the single-phase columns
NEC Article 430.22 — Sizing Motor Branch-Circuit Conductors	NEC 2023 (NFPA 70-2023)	the 125% factor

Cross-checked against:

Every current value checked against the NEC motor full-load current tables
The voltage relationship verified — current falls in proportion to voltage across the three-phase columns
The 125% column recomputed at build time for every row
Five values held as known-value checks across the horsepower range

Derived values — the following values on this page are calculated, not taken directly from the standard:

Value	How it is derived
125% of 460 V current	460 V three-phase full-load current × 1.25, the branch-circuit sizing factor.

Values are Code table figures for general-purpose motors. Specific motor types — synchronous, wound-rotor, direct-current, or motors with unusual characteristics — are covered by different tables or by the manufacturer's data.

Accuracy and use. The values on this page are compiled from the published standards and cross-checked sources listed above. Where values are derived, the derivation is stated. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Every value on this page is traceable to the sources listed above. If you use the data in a document, paper or report, cite it as:

Plain text

Engineering Reference. "Motor Full-Load Current Chart." https://refmanual.com/charts/motor-full-load-current/ (accessed 2026-09-29). Data from NEC Table 430.250 — Full-Load Current, Three-Phase Alternating-Current Motors, NEC 2023 (NFPA 70-2023).

BibTeX

@misc{motor-full-load-current,
  title        = {Motor Full-Load Current Chart},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/charts/motor-full-load-current/}},
  note         = {Accessed: 2026-09-29},
  source       = {NEC Table 430.250 — Full-Load Current, Three-Phase Alternating-Current Motors, NEC 2023 (NFPA 70-2023)}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Motor Full-Load Current Chart
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/charts/motor-full-load-current/
PY  - 2026
DA  - 2026-09-29
N1  - Source: NEC Table 430.250 — Full-Load Current, Three-Phase Alternating-Current Motors, NEC 2023 (NFPA 70-2023)
ER  -

Each row in the tables above also has a permanent link — hover a row and use the # link to cite a single value rather than the whole page.